Indoor Radon Concentrations Research Articles

Radon transport to indoor air in groundwater plants as a by-effect of different water treatments

Radon released from groundwater into indoor air is the main radiation safety problem for water treatment plants. This study investigated the release of radon from different water treatment processes and the effect of ventilation on the indoor radon concentration at six waterworks. In addition to various aeration processes, groundwater pretreatments, such as activated carbon and pre-ozonation, were demonstrated to be associated with the indoor radon concentration. This study revealed that accurate assessment of radon exposure at water treatment plants is very difficult because of the large and sudden temporal variations in the radon concentration and smaller local variations that follow the steps of the water treatment process and ventilation. Based on the study, concrete proposals are also presented for improving radiation safety and the reliability of measurements.

Characteristics of Indoor and Soil Gas Radon, and Discussion on High Radon Potential in Urumqi, Xinjiang, NW China

Urumqi City, located in the northwest of China, is a city with a high indoor radon concentration in a nationwide indoor radon survey in China. This study focuses on the assessment of the indoor radon level and its distribution in this city. Indoor radon measurement using RAD7 and solid nuclear track detector (SSNTD), soil gas radon measured by RAD7, and the determination of the specific activity of uranium and radium in soil samples by a high pure germanium spectrometer were performed from 2021 to 2023. The results reveal a wide range of indoor radon concentrations in Urumqi, with anomalies above 400 Bq/m3 in some dwellings. The arithmetical and geometric mean values of indoor radon concentration are 80 ± 77 Bq/m3 and 58 Bq/m3, respectively. The geometric mean value of radon measured by SSNTD is 101 Bq/m3. The distribution of areas with a high indoor radon concentration is spatially consistent with deep and large active faults or overlapping and intersection zones of multiple groups of faults. It is recommended to conduct a more comprehensive investigation and research into the elevated radon potential and radioactivity associated with building materials.

Investigations of indoor radon levels and its mapping in the Greater Accra region, Ghana

In this work, the indoor radon concentration and radiation dose risks were studied in dwellings within the Greater Accra region, using CR-39 detectors. The indoor radon concentrations ranged from 36.1 ± 2.7 to 92.0 ± 5.2 Bq m−3 with an annual average of 50.8 ± 3.4 Bq m−3. The annual mean effective dose was estimated as 1.3 mSv year−1. Excess lifetime cancer risk and lung cancer cases were assessed with 5% annual lung cancer deaths due to radon was realized. Indoor radon maps created with ArcGIS software over a 5 × 5 km2 grid showed radon prone areas in the region.

Exposure of students (pupils) and employees of educational institutions in the Leningrad region to natural sources of radiation Part 2: Hygienic assessment of doses and health risks depending on methods and approaches to measuring indoor radon concentration

Exposure of students (pupils) and employees of educational institutions in the Leningrad region to natural sources of radiation Part 2: Hygienic assessment of doses and health risks depending on methods and approaches to measuring indoor radon concentration

Radiological Risk Assessment of Radon Inhalation in Offices of Selected Institutions in Southwestern Nigeria

The deleterious health implication of human exposure to radon gas has attracted considerable research attention worldwide. Thus, with the increase in number of tertiary institutions in Nigeria whose population predominantly comprises the youth and adults in their productive years. This study hereby estimates the radiological risk associated with radon inhalation induced by the geological of selected tertiary institutions in Southwestern Nigeria. The radon concentration was assessed with Electret Passive Environmental Radon Monitor (E-PERM). The lithology and age of the buildings were also considered for probable effect on the radon concentration. The value of the radon concentration ranged between 2.60 to 219.57 Bqm-3. The lithology feature on which each building was constructed as well as the age of the building was also found to influence the indoor radon concentration. The radiological indices of the rooms ranged from 0.018 to 1.518 mSvy-1 for annual effective dose (AED), 0.004 to 0.335 WLMy-1 for annual exposure (AE), and 1.98 x 10-6 to 1.67 x 10-4 MPY-1 for excess lifetime cancer risk (ELCR). Hence, there is need for continuous education of the people to take adequate preventive measures in mitigating indoor radon level.

Risk Assessment of Lung Cancer Caused by Indoor Radon Exposure in China during 2006–2016: A Multicity, Longitudinal Analysis

Indoor radon is a well-documented environmental factor as a second cause of lung cancer. Based on the chronological data on indoor radon concentration, lung cancer incidence, and the distribution of sex-age-specific population, the risk of lung cancer caused by indoor radon exposure in a total of 15 cities in China was assessed by using the risk model developed by the U.S. Environmental Protection Agency (EPA) in this study. The estimate revealed that both the excess relative risk (ERR) and lifetime relative risk (LRR) have obviously increased after 2010. The population attributable risk (PAR) in 2016 was estimated in a range from 6.66% to 22.42%, with a median of 15.33% for the 15 cities. The lung cancer incidence attributed to indoor radon in 2016 ranged from 3.96 to 15.07 per 10,000 population in males and 1.21 to 8.27 per 10,000 population in females. Across age and sex, the risk of lung cancer caused by indoor radon was found more pronounced in males and 40-45 age groups. The chronological variation of radon concentrations was considered in this study; the estimate of lung cancer caused by indoor radon in China is considered more reasonable than ever before.

Exploring statistical and machine learning techniques to identify factors influencing indoor radon concentration

Radon is a radioactive gas with a carcinogenic effect. The malign effect on human health is, however, mostly influenced by the level of exposure. Dangerous exposure occurs predominantly indoors where the level of indoor radon concentration (IRC) is, in its turn, influenced by several factors. The current study aims to investigate the combined effects of geology, pedology, and house characteristics on the IRC based on 3132 passive radon measurements conducted in Romania. Several techniques for evaluating the impact of predictors on the dependent variable were used, from univariate statistics to artificial neural network and random forest regressor (RFR). The RFR model outperformed the other investigated models in terms of R2 (0.14) and RMSE (0.83) for the radon concentration, as a dependent continuous variable. Using IRC discretized into two classes, based on the median (115 Bq/m3), an AUC-ROC value of 0.61 was obtained for logistic regression and 0.62 for the random forest classifier. The presence of cellar beneath the investigated room, the construction period, the height above the sea level or the floor type are the main predictors determined by the models used.

Assessment of environmental radiological hazards associated with elevated levels of radon gas in drinking water

The purpose of this study was to assess the environmental radiological hazards associated with elevated levels of radon gas in drinking water. Using passive (CR-39 plastic detector) and active (RAD 7) detectors, the radon levels in the air and drinking water (tap water) of 124 homes in 31 distinct locations in Iraqi Kurdistan were determined. Almost anywhere with a high indoor radon level also has a high radon exhalation rate from drinking water. The cities of Similan and Kelak had the highest and lowest radon concentrations using both techniques. A good correlation was found between the values of the average indoor radon concentration for active and passive detection methods. The values are smaller than the internationally recommended limit of 11 Bq/l as proposed by the Environmental Potential Agency (US EPA).

Indoor radon mitigation strategies: The Alto Minho region (Northern Portugal) practical case

The article explores techniques for mitigating indoor radon in buildings, including soil depressurization, anti-radon coatings and membranes, interior mechanical building pressurization, and natural and forced ventilation procedures. The effectiveness of each technique depends on various factors, such as indoor radon level or building construction type. The region of Alto Minho, Northern Portugal, mostly comprises single-family housing with different structures and materials, and performing an assessment stage is crucial for selecting the appropriate mitigation method. The ageing and declining population in the region suggests that the rehabilitation of existing buildings is more likely than the implementation of new construction. The article also emphasizes the potential impacts of soil depressurization and pressurization on soil geotechnical properties. Anti-radon barriers and mortars have been effectively used in high indoor radon concentration situations and can be combined with natural or forced ventilation procedures and real-time multi-parameter monitoring for improving indoor air quality and energy efficiency of buildings.

RADON MEASUREMENT IN CONSTRUCTION MATERIALS FROM THE NORTHEASTERN REGION OF THAILAND

Indoor radon concentration plays a vital role in the total annual effective dose due to internal radiation exposure. This research investigated the radon gas found in concrete, which consists of rocks, sand, and cement. It can be found in most houses and buildings in Thailand to evaluate the possible residents’ health hazards. Radon was measured using an ionization chamber detector (ATMOS 12 DPX), and the values of the radon concentration, radon exhalation rate, and annual effective dose were calculated. This study collected concrete samples from Loei, Khon Kaen, Nong Bua Lam Phu, Bueng Kan, Nakhon Phanom, Mukdahan, Ubon Ratchathani, and Nakhon Ratchasima provinces in the northeastern region of Thailand. The radon concentration in the concrete samples varied from 22.00 ± 4.00 to 110.00 ± 8.00 Bq⸱m-3, with an average of 56.77 ± 5.77 Bq⸱m-3. These values were below the guideline level of 148 Bq⸱m-3, recommended by the US Environmental Protection Agency (US EPA). The radon exhalation rate varies from 4.20 ± 0.84 to 55.07 ± 4.00 Bq⸱kg-1⸱h-1, with an average of 15.47 ± 1.68 mBq⸱kg-1⸱h-1. The annual effective dose ranges from 0.57 ± 0.10 to 2.89 ± 0.21 mSv⸱y-1, with an average of 1.47 ± 0.15 mSv⸱y-1. The International Commission recommends the dose limit of 1 mSv⸱y-1 for public exposure on Radiological Protection (ICRP).

Indoor radon concentrations in kindergartens in three Bulgarian districts.

This article examines the results of a study of radon concentrations in kindergartens in three districts of north-western Bulgaria. For the period from December 2019 to May 2020, passive radon measurements were accomplished in 1490 premises of 130 kindergartens. The highest arithmetic mean (AM) value of 219Bqm-3 and geometric mean (GM) value of 156Bqm-3 radon concentration were found in the state kindergartens of the Vratsa district. The radon values for the remaining two districts are as follows: Lovech-AM = 156Bqm-3 and GM = 114Bqm-3; Montana-AM = 125Bqm-3 and GM = 88Bqm-3. The effects of various factors on the radon concentration including district, year of building construction, presence of basement, place of premise, wall, and floor interior covering materials, and presence of a ventilation system were investigated. Factor Analysis was used to assess the combined effects of those factors on indoor radon concentration. The results revealed three combinations of the investigated factors: the first combined the district in which the kindergartens were located and the materials used for the floor of the premises, the second combined the year of construction of the building and the presence of a building foundation, and the third combined the rest of the investigated factors. It is concluded that a regional assessment of predictors of radon variability is needed. The walls in kindergartens should not be covered by gypsum, and floors should not be made from materials that can easily develop cracks such as terra cotta. The installation of a ventilation system reduces the radon concentrations in the premises, which is of particular importance in cases where the measured value is above the national reference levels.

Mapping in a radon-prone area in Adamawa region, Cameroon, by measurement of radon activity concentration in soil.

The radon-prone area of the Adamawa region in Cameroon is characterized by high natural radiation background resulting from the high concentrations of radium-226, thorium-232, and indoor radon. To produce a radon-risk map, radon measurements in soil were carried out in the city of Ngaoundere. The radon activity concentration in soil gas ranged from 256 to 166kBqm-3 with a mean of 80kBqm-3 and a standard deviation of 38kBqm-3. The area is mostly classified as high risk (80%) according to the Swedish classification, and 20% as medium risk. A low-risk area was not observed. Granite-like geology sites were characterized by higher radon concentration. A ratio of about 295:1 was obtained for soil radon gas to indoor radon concentrations, with a positive correlation (R = 0.40), and a transfer factor of 3 per mil. These results demonstrate that in situ measurements of radon concentration in soil can provide accurate information on the level of indoor radon concentrations. Geostatistical and deterministic interpolation techniques have been used to obtain a radon map by comparing the suitability of ordinary kriging and inverse-distance-weighted (IDW) interpolation methods. It turned out that there is not much difference in the prediction errors of the two techniques (Root Mean Square Error = 34.4 for ordinary kriging and 34.3 for IDW). It is concluded that both methods give acceptable results. In situ measurements and geostatistical analysis allow assessment of expected indoor radon exposure in a given area at reduced costs and time required. However, for the investigated area, more research is needed to produce reliable radon-risk maps.

Study of radium content and radon exhalation rates in raw building materials used in southern India

As a potential source of indoor radiation arising from radon, a range of building materials (white cement, gray cement, gravel, gypsum, granite, marble, vitrified tile, and brick) were studied for the specific activity of radium and radon gas exhalation rates. The activity of radium was determined using scintillation gamma-ray spectrometry. Exhalation rates were assessed using passive and active measurement methods. Radon mass exhalation rates from powdered building materials and radon surface exhalation rates from slab-type building materials were measured. Activity concentrations of 226Ra in powder and slab-type building materials were found in the range of (1.12 – 14.98) Bqkg−1 and (17 – 308) Bqkg−1, respectively. 222Rn mass exhalation rates (mBqkg−1h−1) from the building materials were in the range of 15.0 ± 0.8 (gray cement) to 1.1 ± 0.1 (gravel). Surface exhalation rates (mBqm−2h−1) for slab-type materials have a range of 317 ± 9 (brick) to 8 ± 2 (marble). Strong positive correlations were found between the specific activity of radium and radon mass exhalation rates (r = 0.9408) and radon surface exhalation rates (r = 0.7167) for building materials investigated. Obtained data indicates that the building materials used influence indoor radon concentration in dwellings.

Indoor Radon Survey in Aksu School and Kindergarten Located near Radioactive Waste Storage Facilities and Gold Mines in Northern Kazakhstan (Akmola Region)

Northern Kazakhstan is considered a field of uranium, gold mining, copper–molybdenum ore, and other metals. The aims of the current work were to monitor the indoor radon levels in a school and a kindergarten and to determine the levels of teacher and student exposure to radon. High radon concentrations were detected in the school on the first floor at ca. 9600 Bq/m3, on the second floor at ca. 6800 Bq/m3, on the third floor at ca. 4900 Bq/m3, and in the kindergarten, the concentration was ca. 9500 Bq/m3. The annual effective dose of the students and teachers of the school and kindergarten varied from 4 mSv/y to 9 mSv/y, which is an order of magnitude higher than the upper annual dose limit. The excess lifetime cancer risk was 14–20% for students, 31.1% for school and kindergarten staff, and 34.9% for kindergarten children. The indoor radon concentrations varied with weather conditions, and it was evident that ventilation had a significant effect on the reduction in the concentration. At these premises, positive correlations between the radon concentrations, outside temperature, and relative humidity were obtained, showing that the concentration of radon is influenced by meteorological parameters. This study will help to identify buildings where continuous monitoring is needed in order to reduce indoor radon levels.

INFLUENCE OF GEOLOGICAL PARAMETERS ON THE INDOOR RADON CONCENTRATION IN THE CITY OF TREBINJE

The paper deals with the analysis of the indoor radon concentration results measured in four schools of Trebinje city and taking into consideration their geological background and its characteristics. There have been 13 measurements and the results showed the range of 75 Bq/m3 to 4244 Bq/m3. Some of the indoor radon concentrations were very high, up to 15 times higher than recommended ones reaching the level of 300 Bq/m3. In each of the four schools there are spots with the high geogenic potential and, 38 % results show a concentration higher than 1100 Bq/m3, which further characterize this area as Radon Priority Area. From the geological point of view, the geological sheet Trebinje represents a part of Mesozoic and Paleogenic complex which build the outdoor Dinarides part. There are also different varieties of calcium carbonate and dolomite areas with sporadic occurrence of sandstones (pescari) and marlstones (laporci) accumulated at the end of the Paleogene period so that lithological content is pretty simple. The main part of the terrain is represented by sediments originated from Mesozoic and Paleogenic structures which appear along with greater dislocation in narrow strings.

Public exposure in the Orenburg region due to natural sources of ionizing radiation. Part 2: Doses to the population of the eastern districts of the Orenburg region

The paper presents the estimated doses to the population of six eastern districts of the Orenburg region, Russia, based on the results of a comprehensive radiation survey conducted in 2019 in 34 settlements with previously found elevated levels of activity concentration of natural radionuclides in tap water from groundwater sources of drinking water supply. It is shown that the average individual annual effective dose due to all natural sources of ionizing radiation in 18 of 34 settlements corresponds to ‘elevated level’ of exposure due to natural sources according to established classification (from 5 to 10 mSv/year), and in another 7 settlements to ‘high level’ (over 10 mSv/year) with radon being the main contributor to the dose. Four settlements of Kvarkensky and Adamovsky districts, where the highest indoor radon concentrations had been found, were selected for a detailed survey, which included measurements of density of radon flux from the soil, radon concentration in soil gas, activity concentration of natural radionuclides in samples of building materials and in soil samples, and activity concentration of radon in tap water from groundwater sources of drinking water supply. Results of the detailed survey proved that the main source of radon in the buildings was the soil gas infiltration; compared to it, the contribution of waterborne radon release was insignificant.

Exposure of students (pupils) and employees of educational institutions in the Leningrad region to natural sources of radiation. Part 1: Results of a comprehensive survey

Currently, there is no methodological support for radiation monitoring and sanitary and epidemiological assessment of radon concentration (or radon EEC) and other parameters of the radiation situation in existing operated buildings. The paper presents a review of the protocols for conducting measurements of indoor Leningrad region with previously found elevated levels of radon concentration using long-term measurements. The survey revealed that highest values of indoor radon ECC were obtained using instant measurements in several educational institutions both in the normal operation mode of the buildings (up to 1106 Bq/m3) and after leaving the premises for 12 hours with closed windows and doors (up to 1586 Bq/m3) according to the requirements of paragraph 6.5 of MU 2.6.1.2838-11. High values of radon concentration were also obtained using long-term and short-term measurements (up to 4900 and 1420 Bq/m3, respectively). In addition, high values of radon flux density were detected (up to 2030 mBq/(m2·s)). The established hygienic norms for ambient dose equivalent rate indoors and outdoors were not exceeded in the surveyed educational institutions. The levels of gross alphaand beta activities in tap water sampled from the surveyed educational institutions were below the control levels, and an exceedance of intervention level for activity concentration of radon in analyzed samples was not detected. The results of the survey will be used for hygienic assessment of doses and health risks for students (pupils) and employees of several educational institutions of the Leningrad region due to exposure to radon and its progeny and can be used to improve the method for indoor radon concentration monitoring in existing operated public buildings in the Russian Federation, which in turn will make it possible to obtain correct values of public doses and health risks.

In-depth study of radon in water in a Greek village with enhanced radon concentrations

This study focused on the radon transfer from the water to the air and the subsequent impact of waterborne radon indoors, taking advantage of the enhanced and decreasing from year to year radon-in-water concentrations observed in the Arnea village in Northern Greece. Some other essential aspects and observations regarding radon-in-water were also discussed. Concerning radon transfer from water to the air, the transfer efficiencies for showering and the use of the bathroom tap were estimated by measuring the radon-in-water and the waterborne radon-in-air concentrations in sealed bathrooms of two apartments in Arnea. The transfer efficiency for the bathroom tap use ranged from 22 to 28.9% for water flow rates of 2.7–7 L min−1. For showering, the transfer efficiency ranged from 45 to 48.3% for water flow rates of 6 L min−1 and 8 L min−1, respectively. As for the impact of waterborne radon indoors, each year's two-week monitoring of radon-in-water and radon-in-air concentrations in a house in Arnea from 2018 to 2022 revealed rapid and sharp increases in the bathroom air related to waterborne radon. Following the results obtained in the house's bathroom in Arnea, showering is the most significant exposure of humans to waterborne radon due to the person's proximity to waterborne radon, the enclosed space, the high transfer efficiency of showering, and the significant amount of water consumed. Each year's two-week average indoor radon concentrations measured in the examined house in Arnea showed that waterborne radon's contribution is less important than the other parameters affecting indoor radon, such as ventilation rates and radon emanation from the soil beneath the house's structure. Time variation (2018–2022) of radon activity concentration measured in a borehole supplying Arnea with water showed a relatively low standard deviation (10.2%) at a coverage factor of k = 1. A disequilibrium was observed between radon and its progenies immediately after pumping water from a borehole. This disequilibrium was observed for 1.3 years and seems to be continuous. Regarding radon removal from water, the diffused bubble aeration System constructed in Arnea reduces the radon-in-water activity concentration by more than 90% when using an air-to-water ratio of 10:1 and a detention time of 60 min. The System does not affect the adjacent outer space radon-in-air concentrations.

Residential radon exposure in Astana and Aqsu, Kazakhstan

A pilot study was carried out to measure indoor radon concentrations in a uranium mining area of northern Kazakhstan. A total of 80 places at kindergartens, elementary schools, and dwellings were selected in Aqsu village and Astana city as the uranium mining area and background area for comparison, respectively. In Astana and Aqsu, the 3-month radon concentrations from late summer to autumn in 2022 were measured using the RADUET passive radon detectors. Radon concentrations ranged from 4 to >2000 Bq m−3 (mean ± standard deviation: 290 ± 173 Bq m−3) throughout the study areas. The concentrations were higher in Aqsu, and 70% of the dwellings there exceeded 300 Bq m−3, whereas only 5% of them exceeded 300 Bq m−3 in Astana. Accordingly, the new dose conversion factor for radon recommended by International Commission on Radiological Protection Publication 137 was applied to calculate the annual effective dose. The annual effective dose from the inhalation of radon was estimated to be 3.6 ± 4.6 mSv y−1 for Astana and 23.7 ± 15.6 mSv y−1, for Aqsu, which are both higher than the world average value of 2.5 mSv y−1.

Experimental Study on CO2 and Radon Mitigations in an Apartment Using a Mechanical Ventilation System

The public interest in indoor air quality has rapidly increased in Korean society, and ventilation systems can play an essential role in improving indoor air quality. This study aims to estimate the reduction in indoor CO2 and radon, which can be effectively mitigated by air exchange, according to the operation of mechanical ventilation in an apartment with the national standard housing size (85 m2) and shape in Korea. The time required to meet Korea’s mandatory indoor CO2 standard (1000 ppm) was 167, 98, 66, and 51 min under air change rates of 0.5, 1.0, 1.5, and 2.0 ACH (air change per hour), respectively. Regarding indoor radon, the removal rate increased with increased ventilation volume, and the minimum concentration level was low and sustained for a prolonged duration. Nonetheless, an air change rate of 0.5 ACH may not offer sufficient ventilation. Additionally, it is imperative to note that indoor radon concentrations tend to escalate swiftly when a mechanical ventilation system is deactivated. Thus, to enhance indoor air quality, it is necessary to reconsider strategies to augment the air change rate and guarantee uninterrupted ventilation.